Design And Implementation Of Transmitting And Receiving Digital Beam Forming System

Digital Beam Forming(DBF) is the result of combining theory of array antenna beam forming and digital signal processing. Compared with traditional beam forming method, DBF has advantages of high precision and flexible manipulation, which can improve the efficiency of beam forming. As the improving in digital signal processing technology, DBF become more and more widely used. In this thesis, transmitting and receiving digital beam forming system is designed and engineering realized, and from principle analysis to engineering realization, the research work concentrates on the following points:1. Proceed from the principle of phased array antenna, the antenna patterns of uniform linear array and planar array are simulated, and the influences of elements’ number, distance between two elements, and operating wavelength on antenna pattern are discussed. At the same time, some different methods of amplitude weighting on reducing side lobe level to improve system performance are discussed in receiving digital beam forming system, such as hanning window, triangle window, taylor window and so on, and according to system requirements, taylor window is selected as the weighted point plan of receiving DBF design finaly.2. With the technology of direct digital synthesis as the core, transmitting DBF system is designed. According to the characteristic of array antenna in multichannel beam forming, the influence of amplitude and phase errors between transmitting channels on beam forming performance. Meanwhile, an open-loop and closed-loop method is designed to calibrate the amplitude and phase errors, and then, these two test method are compared according to actual test process and result.3. The algorithm of receiving DBF is analysed and the design of receiving digital beam forming system is finished based on the hardware of FPGA. On amplitude and phase errors between receiving channels, effective error-calibration is designed, which can test amplitude difference between channels accurately under the condition of ensuring the echoed signals be same, by the method which takes the same T/R as the transmitting terminal and different T/R as the receiving terminal with transmitting signal coupling directly to the channel to be tested.4. Testing methods of antenna patterns are designed, which are used to test the effect of transmitting and receiving digital beam forming respectively. The testing results show that the design proposal of transmitting and receiving digital beam forming system in this thesis is viable.